Aquaculture Europe 2023

September 18 - 21, 2023



A. Arakelyan1,2 *, J. Majstorovic1,3, I. Mladineo1


1Institute of Parasitology, Biology Centre Czech Academy of Sciences, Ceske Budejovice, Czechia

2Erasmus Mundus Joint Master Program in Aquaculture Environment and Society

3 Faculty of Science, University of South Bohemia, Ceske Budejovice , Czechia




 Antimicrobial resistance is a major health issue of this era, affecting the lives of millions of people worldwide. Alternative solutions  have been proposed,  such as the use of host defense peptides (HDPs) ,  which  are vital components of innate immunity, with antibacterial, antifungal, antiviral, and antiparasitic, as well as immunomodulatory properties (Mladineo et al., 2023; Shi et al., 2022). In particular, anisaxins ,  a cecropin-like helminthic HDPs  from the zoonotic marine nematodes, Anisakis simplex and  Anisakis pegreffii , have  shown high efficacy  against clinical and referent human bacterial  Gram-negative isolates (Rončević et al., 2022).

Materials and methods

 In order to evaluate the immunomodulatory properties of  HDP  anisaxin-2S (A-2S), the blood of the common carp  Cyprinus carpio have been  drawn  from  four groups of fish : i ) specific pathogen free fish (SPF); ii) fish infected by  the myxozoan Spaherospora molnari blood stages (BS); iii) fish infected by  S. molnari blood stages and immunosuppressed (IS+BS); and iv) non-infected immunosuppressed fish (IS). B lood  collected at four time points (T0, week 2, 3, and 4) was separated by Ficoll,  and  white  (WBC) and red blood cell (RBC) suspensions were in vitro stimulated by A-2S.  Flow cytometry was used to measure  cellular  changes  and  reactive oxygen species (ROS) production. Gene expression of innate immunity targets ( il6, il10, il1b, tnf α, infγ ) was quantified by qPCR and  log-transformed relative gene expression data was used to test the statistical difference. D ata were analysed in Prism 9 and  presented as mean values ± SD.

Results and discussion

 S. molnari infection decreased the number of RBCs in the blood by approximately 10% (100 × 106 RBC/mL), with  a  significant difference observed 2 weeks post-infection (wpi).  In infected immunosuppressed fish, a steep decline in erythrocyte s (loss of 84%) was observed 3rd wpi onward. On the contrary ,  non-infected but immunosuppressed  fish exhibited mild but significantly  higher numbers of erythrocytes. The decrease of erythrocytes during late-stage infection was accompanied by a release of the erythroblasts.  This indicates a strong interaction of  S. molnari and WBC/RBC as reported earlier (Korytář et al., 2020). H igh activity of both pre- and mature RBC in the IS group suggests that in the absence of the lymphocytes, erythrocytes contribute to an immune response in  a much larger range (Fig. 1). All groups treated with A- S2 showed higher ROS production , in particular the IS+BS group, inferring the immunomodulatory role of this HDP (Fig. 2)


Immunomodulatory properties of the A-2S to the immune response in infected fish are promising, especially if we consider the fact that anisaxin predominantly stimulates red blood cells which are the most abundant population in the blood.


Funded by the European Union under the Horizon Europe Programme, Grant Agreement No. 101084204 (Cure4Aqua). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Research Executive Agency (REA). Neither the European Union nor the granting authority can be held responsible for them.


Korytář , T., Chan, J. T. H., Vancová , M., & Holzer, A. S. (2020). Blood feast: Exploring the erythrocyte‐feeding behaviour of the myxozoan Sphaerospora molnari . Parasite Immunology , 42 (8), pim.12683.

Mladineo , I., Rončević , T., Gerdol , M., & Tossi , A. (2023). Helminthic host defense peptides: using the parasite to defend the host. Trends in Parasitology , 39(5):345-357

Rončević , T., Gerdol , M., Mardirossian , et al . (2022). Anisaxins , helical antimicrobial peptides from marine parasites, kill resistant bacteria by lipid extraction and membrane disruption.  Acta Biomaterialia , 146 , 131–144.

 Shi, G., Kang, X., Dong, et al . (2022). DRAMP 3.0: an enhanced comprehensive data repository of antimicrobial peptides. Nucleic Acids Research , 50 (D1), D488–D496.